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Reconfigurable metasurface lens based on graphene split ring resonators using Pancharatnam–Berry phase manipulation
摘要： A reconfigurable graphene based metasurface is presented to controllably focus a circularly polarized incident plane wave. The unit cell of the proposed metasurface consists of split ring resonators on both sides of a dielectric layer. The required phase shift for focusing purpose is achieved by concurrent rotation of the elements to obey to the Pancharatnam–Berry concept. Convergence/Divergence of the transmitted wave can be controlled by handedness of the impinging plane wave and direction of the elements’ rotation. The operating frequency of the designed lens and its focal length can be adjusted by properly exploiting to the unique property of graphene, i.e. by tuning its chemical potential.
关键词： metasurface,Graphene,Pancharatnam–Berry phase,reconfigurable lens
更新于2025-09-23 15:23:52
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Recipe for Dirac Phonon States with a Quantized Valley Berry Phase in Two-Dimensional Hexagonal Lattices
摘要： The topological quantum states in two-dimensional (2D) materials are fascinating subjects of research, which usually highlight electron-related systems. In this work, we present a recipe that leads to Dirac phonon states with quantized valley Berry phase in 2D hexagonal lattices by first-principles calculations. We show that candidates possessing the three-fold rotational symmetry at the corners of the hexagonal Brillouin zone host valley Dirac phonons, which are guaranteed to remain intact with respect to perturbations. We identify that such special topological features populated by Dirac phonons can be realized in various 2D materials. In particular, the monolayer CrI3, an attractive 2D magnetic semiconductor with exotic applications in spintronics, is an ideal platform to investigate nontrivial phonons in experiments. We further confirm that the phonon Berry phase is quantized to ±π at two inequivalent valleys. The phonon edge states terminated at the projection of phonon Dirac cones are clearly visible. This work demonstrates that 2D hexagonal lattices with attractive valley Dirac phonons will extend the knowledge of valley physics, providing wide applications of topological phonons.
关键词： Dirac phonons,first-principles calculations,valley Berry phase,phonon edge states,2D hexagonal lattices
更新于2025-09-23 15:21:21
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Berry phase in strained InSb whiskers
摘要： Strain influence on the longitudinal magnetoresistance for the n-type conductivity InSb whiskers doped by Sn to concentrations 6·1016–6·1017 сm–3 were studied at temperatures from 4.2 to 50 K and magnetic field up to 10 T. The Shubnikov–de Haas oscillations at low temperatures were revealed in the strained and unstrained samples with all range doping concentration. Some peaks of the longitudinal magnetoresistance split as a doublet in the InSb whiskers with doping concentration in the vicinity to metal-insulator transition. Taking into account peak splitting giant g-factor from 30 to 60 was defined for strained and unstrained samples. The magnetoresistance oscillation period of the InSb whiskers doesn’t differ under strain for all doping concentration, but Fermi energy increases and electron effective mass mс decreases and consists 0.02 m0. Berry phase presence was also revealed in strained n-InSb whiskers that shows their transition under a strain to topological insulator phase.
关键词： Berry phase,topological insulator,strained InSb whiskers,Shubnikov–de Haas oscillations,magnetoresistance
更新于2025-09-23 15:21:21
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Generation of pure Laguerre-Gaussian vector beams on the higher-order Poincaré sphere by hollow Gaussian beams through dielectric metasurfaces
摘要： It is a longstanding challenge for the extracavity generation of vector beams (VBs) to have pure Laguerre-Gaussian (LG) modes due to diffraction. Here we propose theoretically and realize experimentally the generation of pure LG VBs by using hollow Gaussian beams (HGBs) through q-plates. A general expression for the VB generated by the HGB with arbitrary polarization is derived. It is found that when the order of the HGB is two times the topological charge of the q-plate, the VB possesses a pure LG mode and that any desired polarization distribution on the higher-order Poincaré sphere can be realized by tuning the incident polarization. Further we implement the q-plates with dielectric metasurfaces and experimentally verify the theoretical results. The generated pure LG VB may find applications in the situations where high mode purity is required.
关键词： Vector beam,Laguerre-Gaussian mode,Diffraction,Metasurfaces,Pancharatnam-Berry phase,Hollow Gaussian beam
更新于2025-09-19 17:15:36
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Transition between Electron Localization and Antilocalization and Manifestation of the Berry Phase in Graphene on a SiC Surface
摘要： It is shown that the transport properties of graphitized silicon carbide are controlled by a surface graphene layer heavily doped with electrons. In weak magnetic fields and at low temperatures, a negative magnetoresistance is observed due to weak localization. A crossover in the magnetoresistance from weak localization to weak antilocalization (the latter is the manifestation of the isospin in graphene) is observed for the first time in samples of this kind at elevated temperatures. A pronounced pattern of Shubnikov–de Haas oscillations is observed in strong magnetic fields (up to 30 T). This pattern demonstrated fourfold carrier spectrum degeneracy due to the double spin and double valley degeneracies. Also, the manifestation of the Berry phase is observed. The effective electron mass is estimated to be m* = 0.08m0, which is characteristic of graphene with a high carrier concentration.
关键词： weak localization,Berry phase,graphene,Shubnikov–de Haas oscillations,silicon carbide,magnetoresistance,weak antilocalization
更新于2025-09-11 14:15:04
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Accurate Formula for the Macroscopic Polarization of Strongly Correlated Materials
摘要： The many-body Berry phase formula for macroscopic polarization is approximated by a sum of natural orbital geometric phases with fractional occupation numbers accounting for the dominant correlation effects. This formula accurately reproduces the exact polarization in the Rice?Mele?Hubbard model across the band insulator?Mott insulator transition. A similar formula based on a reduced Berry curvature accurately predicts the interaction-induced quenching of Thouless topological charge pumping.
关键词： natural orbital geometric phases,Rice?Mele?Hubbard model,Berry phase,macroscopic polarization,band insulator?Mott insulator transition,Thouless topological charge pumping
更新于2025-09-09 09:28:46
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Liquid crystal Pancharatnam-Berry phase lens with spatially separated focuses
摘要： In this paper, we proposed and fabricated a liquid crystal (LC) lens with spatially separated focuses via liquid crystal photoalignment technology. The novel lens is an integration of the polarisation grating and conventional LC lens. The two focuses of that new lens, one of which is real while the other is virtual, can be spatially separated. When combined with normal convex lens and illuminated by a linearly polarised beam, the two emergent light beams become all convergent and the two focuses are separated in three-dimension space. Moreover, the focal lengths of the lens system can be artificially controlled by adjusting the distance between our new lens and the conventional lens. Our results achieve the potential of LC lens’ application in imaging devices such as multifocal cameras, bifocal eyeglasses and so on.
关键词： lens,Pancharatnam-Berry phase,Liquid crystal
更新于2025-09-09 09:28:46
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Information Encoding with Optical Dielectric Metasurface via Independent Multichannels
摘要： Information encryption and security is a prerequisite for information technology which can be realized by optical metasurface owing to its arbitrary manipulation over the wavelength, polarization, phase and amplitude of light. So far information encoding can be implemented by the metasurface in one-dimensional (1D) mode (either wavelength or polarization) only with several combinations of independent channels. Herein, we design dielectric metasurfaces by multiplexing for information encoding in a two-dimensional (2D) mode of both wavelength and polarization. 63 combinations made out of six independent channels by two circular polarization states (RCP and LCP) and three visible wavelengths (633 nm, 532 nm and 473 nm) are experimentally demonstrated, in sharp contrast with 7 combinations by 3 independent channels in 1D mode. This 2D mode encoding strategy enhances the encryption security dramatically and paves a novel pathway for escalating the security level of information in multichannel information encryption, anti-counterfeiting, optical data storage, and information processing.
关键词： Pancharatnam-Berry phase,photon spin-dependent state,multichannel,information processing,multiwavelength,dielectric metasurface
更新于2025-09-04 15:30:14